Your house is wired for networking and you probably don't even know it. Wires are wires, and the ones that give you power outlets every six feet aren't much differen than the ones connecting your modem to your network. They're already in the walls and can carry data as well as power, so think about using this Belkin Ethernet-to-powerline conversion hub to let you utilise the wiring you already have, converting the digital signals from up to three devices and transferring it through your house via a "powernet" to other devices.
You can network gaming systems or computers just as if they were wired. The downside is that they cost US$180, and you'll need at least two of them to make it work. The price will probably come down, but for now these types of hubs are great for those who can't wire their homes and can't use Wi-Fi. [Powerline AV+, via Slippery Brick]